countdown UILabel not get decremented

Question

I am trying to make a count down label, But it is not getting decremented..Can any one spot out the error in code

- (IBAction)start:(id)sender
{
     timer = [NSTimer scheduledTimerWithTimeInterval: 1.0 target:self   selector:@selector(updateCountdown) userInfo:nil repeats: YES];
}

-(void) updateCountdown
{
     int hours, minutes, seconds;
     int secondsLeft = 30;
     hours = secondsLeft / 3600;
     minutes = (secondsLeft % 3600) / 60;
     seconds = (secondsLeft %3600) % 60;
     countDownlabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d", hours, minutes, seconds];
}

Answer 1

Because each time when timer fires you use same value for seconds int secondsLeft=30;

You must set value for secondsLeft on starting Timer and decrement it on timer

- (IBAction)start:(id)sender{

  timer = [NSTimer scheduledTimerWithTimeInterval: 1.0 target:self   selector:@selector(updateCountdown) userInfo:nil repeats: YES];

  secondsLeft=30;
 }

 -(void) updateCountdown {
    int hours, minutes, seconds;

    secondsLeft--;
    hours = secondsLeft / 3600;
    minutes = (secondsLeft % 3600) / 60;
    seconds = (secondsLeft %3600) % 60;
    countDownlabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d", hours, minutes, seconds];

Answer 2

You can declare secondsLeft and timer as ivars, decrement secondsLeft every time updateCountdown is called and invalidate the timer when there are no seconds left to decrement.

- (IBAction)start:(id)sender
{
    secondsLeft = 30;
    timer = [NSTimer scheduledTimerWithTimeInterval: 1.0 target:self   selector:@selector(updateCountdown) userInfo:nil repeats: YES];
}

- (void) updateCountdown
{
    int hours, minutes, seconds;

    hours = secondsLeft / 3600;
    minutes = (secondsLeft % 3600) / 60;
    seconds = (secondsLeft %3600) % 60;
    countDownlabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d", hours, minutes, seconds];
    secondsLeft--;

    if (seconds==0)
    {
        [timer invalidate];
    }
}

Answer 3

You have assigned int secondsLeft=30; in your updateCountdown method that's normal.

You should set the initial value of secondLeft somewhere else and then in your method updateCountdown you need to decrement it's value

 -(void) updateCountdown {
    int hours, minutes, seconds;

    hours = secondsLeft / 3600;
    minutes = (secondsLeft % 3600) / 60;
    seconds = (secondsLeft %3600) % 60;
    countDownlabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d", hours, minutes, seconds];
    if (secondsLeft > 0) secondsLeft--;
}

Answer 4

I found the problem...

-(IBAction)start:(id)sender{


countDownView.hidden=NO;

timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(updateElapsedTime) userInfo:nil repeats:YES];
secondsLeft=30;

}



 -(void) updateCountdown {
int hours, minutes, seconds;


hours = secondsLeft / 3600;
minutes = (secondsLeft % 3600) / 60;
seconds = (secondsLeft %3600) % 60;
countDownlabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d", hours, minutes, seconds];

}